RU2614021C1 - Method of producing nickel-63 radionuclide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes heating the metallic nickel-containing radionuclide ⁶³Ni up to its evaporation temperature in a vacuum chamber, a target three-selective photoionization of Ni isotope atoms by means of simultaneous pulsed irradiation of the atoms by spatially combined laser beams with a wavelength of 3222.566±0.001Å, 5464.006±0.001Å and 5442.195±0.001Å with the subsequent isolation of the photoions ⁶³Ni by electric field. The method is carried out at a pulsed laser beam frequency of 5-20 kHz with a pulse duration of 20-100 nsec, and the average laser radiation pulse power density of the first stage is selected in the range 40÷100 mW/cm², of the second stage - 5÷40 mW/cm², of the third stage - 3÷5W/cm² at a pulsed laser beam frequency of 10 kHz with the pulse duration of 20 nsec.

EFFECT: possibility of implementing the method allowing to carry out the simultaneous selection of highly-enriched radionuclides and applying it to substrates at a commercial scale.

4 cl, 2 dwg

Description

FIELD OF THE INVENTION

The invention relates to a method for laser separation of the ⁶³ Ni isotope using photoionization of the target isotope, followed by extraction of the ionized target isotope for use in stand-alone power sources, including those based on the betavoltaic effect.

State of the art

Nickel radionuclide ⁶³ Ni, which is a pure beta emitter with a half-life of more than 100 years, is one of the most promising radionuclides for creating miniature autonomous sources of electrical energy with a life of more than 30 years, operating on the beta-voltaic effect [Yu.N. "Modern aspects of the application of the beta-voltaic effect" - Ulyanovsk: UlGPU, 2012; Pustovalov A.A., Gusev V.V., Zadde V.V., Petrenko N.S., Tikhomirov A.V., Tsvetkov L.A. “Nickel-63 Beta-Voltaic Current Source” - “Atomic Energy”, vol. 103, no. 6, December 2007].

Natural nickel consists of five stable isotopes with the following prevalence: ⁵⁸ Ni - 68.07%; ⁶⁰ Ni - 26.22%; ⁶¹ Ni - 1.14%; ⁶² Ni - 3.63%; ⁶⁴ Ni - 0.93%.

A known method of producing a radionuclide ⁶³ Ni, comprising the following sequence of operations: obtaining enriched in ⁶² Ni source material using centrifugal separation, irradiating it in a reactor, conversion to a volatile compound, followed by enrichment in radioisotope ⁶³ Ni (LJ Sosnin, IA Suvorov, AN Tcheltsov, BI Rogozev, VI Gudov Production of ⁶³ Ni of high specific activity. Nuclear Instruments and Methods in Physics Research, 1993, v. A334, p. 43-44.

Also known patent RU No. 2313149 (op. 20.12.2007, IPC G21G 1/06, B01D 59/20) "Method for producing radionuclide nickel-63." Provided that the target is enriched in ⁶² Ni to a level of 50%, the content of ⁶³ Ni in the final product can reach 50%. To further increase the concentration of the target isotope, additional centrifugation is required, however, due to the high radioactivity, this process becomes technically difficult to implement.

Also known is the "Method for the production of nickel-63 radionuclide", patent RU No. 2561378 (op. 08.28.2015, IPC G21G 1/00, G21G 4/00, B01D 59/00).

The invention relates to a reactor technology for producing radionuclides and can be used for the production of ⁶³ Ni radionuclide, which is the basis for the creation of miniature autonomous sources of electric energy with a long service life, working on the beta-voltaic effect. A method of producing a ⁶³ Ni radionuclide includes the manufacture of a nickel target enriched in the ⁶² Ni isotope from a composite material consisting of nickel nanoparticles or its compounds surrounded by a buffer in the form of a solid soluble in water or other solvents, irradiating the target in a neutron stream of a nuclear reactor, separation of the target and buffer nanoparticles, the direction of the buffer for radiochemical processing to isolate the ⁶³ Ni radionuclide, and the return of nickel nanoparticles to the nuclear reactor as a new target. The invention provides an increase in the specific activity of the ⁶³ Ni radionuclide, a simplification of the process for its production and a decrease in the amount of radioactive waste.

The well-known "Method for the production of nickel-63 radionuclide for beta-voltaic current sources", patent RU No. 2569543 (IPC G21G 1/00, G21G 4/00, B01D 59/00, op. 27.11.2015).

The invention relates to the field of production of radioactive isotopes, and more particularly to a technology for producing a radioactive isotope nickel-63 used in the production of beta-voltaic current sources. The method for producing the nickel-63 radionuclide includes the production of a nickel-rich nickel target with a nickel-64 content of more than 2% from the original nickel, irradiating the target in the reactor and then enriching the irradiated product with nickel-63 to reach 75% or more in an enriched product. The invention provides large-scale, cost-effective production of nickel-63 for beta-voltaic current sources.

The disadvantage of the above methods is the need for centrifugal isotope enrichment of irradiated radioactive nickel. Working with a highly active gaseous substance leads to contamination of the separation equipment, the constant danger of leaks and is technically difficult.

Known laser photoionization methods for the separation of radionuclides of various isotopes, for example, thallium, ytterbium (patents No. 2317847, 2446003), but these methods are not suitable for use to obtain the ⁶³ Ni isotope.

Disclosure of invention

The technical result to which the invention is directed is the development of a method for isolating a ⁶³ Ni radionuclide with a low degree of radioactive contamination, which can be used on an industrial scale.

,

и

с последующим выделением фотоионов ⁶³Ni электрическим полем.To achieve this result, a method for producing a nickel-63 radionuclide is proposed, comprising heating metallic nickel containing a ⁶³ Ni radionuclide to its evaporation temperature in a vacuum chamber, three-stage selective photoionization of atoms of the target ⁶³ Ni isotope by simultaneous pulsed irradiation of atoms by spatially aligned laser beams with a wavelength

,

and

followed by the separation of ⁶³ Ni photoions by an electric field.

Besides,

- the pulse repetition rate of the laser beams is 5-20 kHz with a pulse duration of 20-100 ns;

- the average power density of the laser radiation of the first stage is selected in the range of 40 ÷ 100 mW / cm ² , the second stage is 5 ÷ 40 mW / cm ² , the third stage is 3 ÷ 5 W / s with a pulse repetition rate of laser beams of 10 kHz with a pulse duration 20 ns;

- the selection of ⁶³ Ni photoions by an electric field is carried out on a collector located in a vacuum chamber.

In FIG. Figure 1 shows the scheme of nickel photoionization through the autoionization state (AIS), which allows one to achieve high efficiency and selectivity in the separation of the ⁶³ Ni radionuclide. The energy levels and wavelengths (vacuum) correspond to ⁵⁸ Ni.

- CTC(⁶¹Ni);

- CTC(⁶³Ni)).In FIG. Figure 2 shows the isotopic structure of the 3d84s2 3F4 → 3d94p 1Fo3 transition. Labels show transition wavelengths for even NiI isotopes; (

- CTC ( ⁶¹ Ni);

- CTC ( ⁶³ Ni)).

The method is as follows.

The starting material is a target of metallic nickel with a certain content of ⁶³ Ni radionuclide. The method of obtaining ⁶³ Ni does not matter. In particular, it is possible to produce a ⁶³ Ni radionuclide by irradiating natural nickel with a neutron flux in a reactor. In this case, the ⁶² Ni nucleus absorbs the neutron and turns into ⁶³ Ni. The higher the initial concentration of ⁶³ Ni, the higher the productivity of the method at equal concentrations of ⁶³ Ni in the product.

The first stage of the process is that metallic nickel is evaporated in a vacuum. A vacuum is necessary in order to prevent oxidation of metallic nickel, and also in order to minimize collisions of nickel atoms with residual gas atoms. Typical residual gas pressures of 10 ^-5 ÷ 10 ^-9 mmHg Marked evaporation of nickel occurs when it is heated to a temperature of 1600 ÷ 1700 ° C. The method of heating does not matter. The general principles of the method for producing various isotopes using this method have been sufficiently developed, see, for example, patents Nos. 2317847, 2446003. An atomic beam with a divergence of 5–20 ° is cut out from the evaporation stream using diaphragms. Thus, a collisionless flow of nickel atoms with a small divergence is formed. Typical values of the density of atoms in a stream are 10 ¹¹ ÷ 10 ¹⁴ atoms / cm ³ .

The second stage of the process is the selective photoionization of ⁶³ Ni atoms in the working volume of the vacuum chamber. To implement photoionization of nickel atoms, a three-stage photoionization scheme has been developed (see Fig. 1).

возможны три перехода: 7/2-7/2, 7/2-5/2 и 9/2-7/2. Длина волны второго и третьего переходов

практически совпадают. Интенсивность перехода 7/2-7/2 с длиной волны

уступает интенсивности двух других переходов почти на порядок. Структура переходов первой ступени представлена на фиг. 2.As the initial level, the ground state of nickel 3d84s2 3F4 is used, the population of which at a temperature of 1700 ° С is 0.42. In accordance with the rules of addition of moments, the hyperfine structure of the ground state of the 63Ni atom with a spin moment of the nucleus 1/2 consists of two sublevels corresponding to the total moment F = 7 / 2,9 / 2. Similarly, the first excited state of 3d94p 1Fo3 is split into two sublevels with the total momentum values F = 5 / 2.7 / 2. Between the ground and first excited states in accordance with the selection rules

Three transitions are possible: 7 / 2-7 / 2, 7 / 2-5 / 2 and 9 / 2-7 / 2. Wavelength of the second and third transitions

almost coincide. Transition intensity 7 / 2-7 / 2 with wavelength

inferior to the intensity of the other two transitions by almost an order of magnitude. The transition structure of the first stage is shown in FIG. 2.

). В качестве второй ступени используется переход из состояния 3d94p 1Fo3 (подуровни 5/2 и 7/2) во второе возбужденное состояние 3d9 4d 2[7/2]4 (подуровни 5/2 и 7/2, длина волны

). Фотоионизация осуществляется за счет перехода из второго возбужденного состояния в автоионизационное с энергией 67707.610 см^-1 (длина волны

). Для осуществления трехступенчатой фотоионизации необходимо одновременное воздействие на атомы лазерного излучения первой, второй и третьей ступени.The wavelengths of the transitions 7 / 2-5 / 2 and 9 / 2-7 / 2 fall into the gap between the absorption wavelengths of stable nickel isotopes ⁶⁴ Ni (frequency distance 750 MHz) and 62Ni (frequency distance 1210 MHz) and this allows excitation and subsequent photoionization with high selectivity. The use of coincident transitions 7 / 2-5 / 2 and 9 / 2-7 / 2 allows all atoms in the ground state to be involved in the photoionization process, which contributes to the achievement of high photoionization efficiency. Thus, the three-stage 63Ni selective photoionization scheme consists in using the 3d84s2 3F4 (sublevels 7/2 and 9/2) as the first step of the transition to the first excited state 3d94p 1Fo3 (sublevels 5/2 and 7/2, wavelength

) As the second stage, we use the transition from the 3d94p 1Fo3 state (sublevels 5/2 and 7/2) to the second excited state 3d9 4d 2 [7/2] 4 (sublevels 5/2 and 7/2, wavelength

) Photoionization is carried out due to the transition from the second excited state to the autoionization state with an energy of 67707.610 cm ^-1 (wavelength

) For the implementation of three-stage photoionization, simultaneous exposure to the atoms of laser radiation of the first, second and third stages is necessary.

For the implementation of selective photoionization, pulsed pulsed dye lasers tuned along the wavelength are used. In particular, it is possible to pump with copper vapor lasers. Typical pulse repetition rates are 10 kHz, and pulse durations are 20 ns. In this case, for effective and selective photoionization, the average power density of the laser radiation of the first stage should be in the range of 40 ÷ 100 mW / cm ² , the second stage - 5 ÷ 40 mW / cm ² , the third stage - 3 ÷ 5 W / cm ² . With these parameters, photoionization is saturated, and the selectivity of photoionization exceeds 1000.

Lasers with a pulse frequency of 5 kHz or 20 kHz can be used. When using lasers with a reduced frequency, it is necessary to proportionally increase the length of the working volume in order to ensure the probability of radiation of atoms. When pumped by solid-state lasers, the pulse duration can reach 100 ns.

The resulting stream of nickel atoms is irradiated with pulsed laser radiation, which is three laser beams with different wavelengths, combined spatially (in one beam) and in time (simultaneous arrival of pulses). A typical beam diameter is 5–30 mm. The average path length of atoms during the time between two pulses at a pulse repetition rate of 10 kHz is 5 cm; therefore, to increase the probability of irradiation of atoms by pulsed laser radiation, it is advisable to increase the size of the irradiation region along the atomic flux to 7-9 cm. radiation through a beam of atoms due to reflection with the help of mirrors of a laser egret at the end of the working volume. The reflected beam is directed back to the working volume with a slight offset so as to irradiate areas of the working volume that were not irradiated during the first passage of the beam. Similarly, the third, fourth and all subsequent passages of the laser beam are formed.

The third stage is the separation of ⁶³ Ni photoions by an electric field.

The separation of the formed ⁶³ Ni photoions can be carried out, for example, directly onto a product collector located in a vacuum chamber. The product collector may be a plate of conductive material of arbitrary shape. To pull positively charged photoions onto the collector, a negative voltage should be applied to surrounding objects. To increase the field strength, it is possible to place a grounded or positively charged electrode nearby the collector. Typical field strengths are 10-100 V / cm. As a result of the extrusion of photoions on the collector plate, a film of metallic nickel enriched with the radionuclide ⁶³ Ni is formed. A collector plate with a sprayed ⁶³ Ni radionuclide film can be removed from the vacuum chamber and used as an element in a power source.

All specific parameters of the method are selected from the capabilities of the equipment and are determined in each case.

Thus, a method is proposed for producing nickel-63 by the photoionization method with high selectivity, the implementation of which will allow producing this isotope in one production cycle, which is in demand on an industrial scale, in particular, for the production of autonomous power sources.

Claims (4)

1. A method of producing a nickel-63 radionuclide, comprising heating metallic nickel containing a ⁶³ Ni radionuclide to its evaporation temperature in a vacuum chamber, three-stage selective photoionization of atoms of the target ⁶³ Ni isotope by simultaneous pulsed irradiation of atoms by spatially aligned laser beams with a wavelength of 3222.566 ± 0.001

, 5464.006 ± 0.001

and 5442.195 ± 0.001

followed by the separation of ⁶³ Ni photoions by an electric field. 2. The method according to p. 1, characterized in that the pulse repetition rate of the laser beams is 10 kHz with a pulse duration of 20 ns. 3. The method according to p. 1, characterized in that the average power density of the laser radiation of the first stage is selected in the range of 40 ÷ 100 mW / cm ² , the second stage is 5 ÷ 40 mW / cm ² , the third stage is 3 ÷ 5 W / cm ² . 4. The method according to p. 1, characterized in that the selection of photoions ⁶³ Ni by an electric field is carried out on a collector located in a vacuum chamber.

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